Method of securing coil ends



Apr 1964 w. J. DE GAIN 3, 90

METHOD OF SECURING con. ENDS Original Filed Dec. 9, 1960 2 Sheets-Sheet 1 7 2M 5 T116 [NI/mm;

l 3 lulu ni 1 1 4 fF-IILJQ BY April 28, 1964 w. J. DE GAIN METHOD OF SECURING COIL ENDS Original Filed Dec. 9, 1960 2 Sheets-Sheet 2 United States Patent I 3,130,490 METHOD OF SECURENG COILENDS William J. De Gain, Detroit, Mich, assignor to "Koppy Tool and Die Company, Ferndale, Mich. Continuation of application Ser. No. 74,319, Dec. 9, 1960. This application Mar. 4, 1963, Ser. No. 262,781 1 Claim. (Cl. 29432) This invention relates to a method of securing coil ends and particularly, a method for interconnecting the ends of two metal strips. This application is a continuation Of'my prior application, Serial No. 74,819, filed December 9, 1960, and now abandoned.

In stamping metal parts from long strips or coils of sheet metal, it is desirable to connect the trailing end of the strip being processed to the leading end of the next, fresh strip, to maintain continuity in the stamping operation.

Hence, it is an object of this invention to provide a method for interconnecting the ends of two strips using a single male and female punching die set, by'fir'st punching a tab opening in the end of one strip and then by using the punched tab opening, as if it were a female punching die half, in cooperation with the male die half to punch a tab on the other strip and to simultaneously lock the tab Within the tab opening, thus tightly and accurately interconnecting the strip ends despite that the dies may be Worn or that the strips may not be accurately aligned initially.

This and other objects and advantages will become apparent upon reading the following description of which the attached drawings form a part.

In the drawings:

FIG. 1 is a schematic, elevational view, partially in section, illustrating the step of positioning the end portion of one coil strip between a pair of punching dies, in a press, for punching a tab opening.

FIG. 2 is a fragmentary, cross-sectional view taken in the direction of arrows 2-2 of FIG. 1.

FIGS. 3 and 4 are cross-sectional views taken in the directions of arrows 33 and 4-4, respectively, of FIG. 1.

FIG. 5 is a cross-sectional view taken in the direction of arrows 55 of FIG. 6.

FIG. 6 is a view, similar to FIG. 1, showing the completion of the first step of punching the tab opening and trimming the coil end.

FIG. 7 is a view showing the step of placing the end of a second coil strip upon the punched and trimmed end of the first coil strip.

FIG. 8 shows the step of simultaneously punching the tab in and trimming the edge of the second coil end and interlocking the tab with the tab opening.

FIG. 9 is a view taken in the direction of arrows 99 of FIG. 8 and shows the connected coil endsv FIG. 10 shows a modified form of tab and tab opening.

The Apparatus FIG. 1 schematically shows a conventional, hydraulic or mechanical press which includes a bed 11 upon which is fastened a female punch die half 12 having a dovetailed type tab opening 13 and a trimming edge 14 (see FIG. 3). The press includes a power operated platen 15 arranged above the bed 11 for movement towards and away from the bed. A male punch die half 16 is secured to the platen 15 by fasteners 17. A tab shaped cutting head 18 and a transverse trimming edge 19 is formed on the male die half.

A conventional stripper block 20 is positioned beneath and is secured to platen 15 by bolts 22 having heads which are movably positioned within bores 23 and having lower ends threadedly engaged with the stripper block at 3,130,49h Patented Apr. 28,1964

21. The block is normally spaced from the lower surface of the platen by coil springs 24 whose upper ends fit within bores 25 formed in the platen and whose lower ends fit within bores 26 formed in the stripper block. The block also includes a tab shaped'opening 27 shaped to receive the cutting head 18 of male diehalf 16 (see FIG. 2).

When the platen 15 is raised relative to the bed 11, the stripper block is suspended from the platen by-its bolts 22. When the platen is lowered, the block presses against the workpiece W, located upon the female die 12, and holds it in place upon the female die until shortly after the male die is raised therefrom by upward movement of the platen.

As shown in FIGS. 3 and 4, the lower end of the tabshaped opening 13 formed in the female die 12 is widened into a side opening slot 28 (see FIG. 1) to permit removal of the portions severed from the end of the coil strip.

The'Method Before starting operation, bolts 22 are adjusted until the space 29 between the platen and the stripperblock 20 is equal to the thickness of the strip. Thus, the'distance that the male die moves downwardly into the female die is equal to the thickness of the strip.

The trailing edge of a coil strip W (which is being fed to the left in FIG. 1) is placed uponthe female die half 12 (see FIG. 1). Next, the platen 15 is lowered (see FIG. 6) and the male die half 16 cooperates with the female die half to punch, in one stroke, a dovetail-shaped slot or opening 30 having a reduced throat portion 31, in the strip W, while simultaneously trimming the rough end of the strip into a sharp, transverse abutment edge 32. The scrap material S drops downwardly and is removed by pulling it sideways (to the right).

Then the platen is raised until the male punch clears the strip and until the stripper block 20 clears the strip and is spaced above it. The strip W is retained in its position, upon the female die half, either manually or by a suitable clamping means, not shown.

Thereafter, the leading edge of the next coil strip W is laid over the already punched trailing edge of strip W (see FIG. 7) and the platen is again lowered (see FIG. 8). The already punched opening 36 and trimmed edge 32 now act as the female die half or as a cap over the female die half. Thus, the male die half punches, in one stroke, the tab 33 and trimmed edge 34 in strip W in cooperation with the already punched strip. Due to the restriction on downward movement of the male die, caused by the stripper block pressing against the upper strip W, the male die stops in the plane of the upper surface of the lower strip W after forcing the tab 33 into opening 30 and thereby interlocks and aligns the strip ends in the same single punching stroke.

Hence, it can be seen that this is a one position operation where the female die half is used once and the male die half twice. The resulting interlock will be accurate even if the dies are worn or if the strips are slightly misaligned. When inaccuracies occur in punching the first strip, corresponding inaccuracies then occur in the second strip because the first strip functions as a female die for the second strip, thereby guaranteeing the desired strong, tight interlock.

When punching the second strip W, there is a spalling or flowing of material to mechanically interlock the contacting edges of the tab and opening and the trimmed edges. Further, because of the greater distance XX at the wider part of the tab, than at YY at the throat, any relative twisting of the strips after they are joined, will result in yielding or twisting at the throat while maintaining the interlock at the wide part of the tab.

The shape of the tab and opening may be varied as 3 illustrated for example, in FIG. 10, where strips C and C are formed with a rounded dovetail tab opening 35 and corresponding tab 36, respectively.

This invention may be further developed into the scope of the following attached claim. Accordingly, it is desired that the foregoing description be read as being merely illustrative of an operative embodiment of this invention.

I now claim:

A method for interconnecting two metal strips, each having a flat, undeformed edge portion, in edge to edge abutting, coplanar relationship by means of a coplanar dovetail shaped tab, formed on the abutting edge of the first strip, interfitted and frictionally locked within a correspondingly dovetail shaped tab opening formed in the portion of the second strip adjacent its abutting edge, using a single male die punch spaced a short distance from and in cooperating punching relationship with a single female die having a punching surface and shaped to receive the male die punch, with the male die punch and female die being shaped to simultaneously punch the tab opening and the strip abutting edge at which the opening is formed, comprising essentially the steps of:

(a) placing and holding the edge portion of the second strip directly upon the punching surface of the female die between the punch and female die;

(b) moving the punch towards and into the female die a sulficient distance to completely sever said edge portion, with one stroke, into the form of a completed dovetail shaped tab opening and the abutting edge of the second strip and a removed scrap edge portion;

(c) continuing to hold the second strip, without moving it, upon the female die punching surface while moving the punch back to its original position away from the female die;

(d) and while continuing to hold the second strip Without moving it, placing the edge portion of the first strip in overlapping position upon the edge portion of the second strip;

(e) again moving the punch towards the female die until the punch is spaced from the female die punching surface a distance equal to the thickness of the second strip, with the punched opening and the abutting edge of said second strip acting as the femaledie cooperating with the punch in completely severing the previously undeformed, edge portion of the first strip into the form of the dovetail shaped tab and abutting edge of the first strip and a removed scrap edge portion of the first strip, while the punch simultaneously presses the tab into the tab opening and presses the two strips into coplanar edge to edge, joined relationship;

(1) then moving the punch away from the female die and removing the now joined strips therefrom.

References Cited in the file of this patent UNITED STATES PATENTS 1,504,464 Douglas Aug. 12, 1924 2,123,626 Fiegel July 12, 1938 2,949,088 Johnson Aug. 16, 1960 

